Hi Samson,
I used Vallejo one 2 or 3 times and went back to Tamiya Fine Surface one without hesitation.IMHO Tamiya Light Grey is the best primer out there , even if its on pricey side. What struck me with Vallejo primer, it didnt last very long , and texture was a bit more grainy.Really made a difference on 54mm's . Now trying Red Oxide Tamiya -its also great but I would nt use it on flesh I use it strictly for base terrains and large flat surfaces . But these are just my personal experiences.
Cheers,
Peter.